The Secondary Conditioned Response of Rats and the Effects of Some Psychopharmacological Agents

Rats trained in an avoidance task developed a secondary conditioned response. Testing seventeen drugs showed that chlorpromazine, promazine, reserpine, and morphine blocked both the primary and secondary avoidance responses at doses that did not impair motor function. Meprobamate, hydroxyzine, azacyclonol, phenaglycodol, and phenobarbitone sodium specifically suppressed only the secondary response without affecting the primary avoidance response. Mescaline and iproniazid also produced a specific depression of conditioned behavior. Barbitone sodium, glutethimide, L1458, and mephenesin inhibited conditioned responses only at neurotoxic doses. These findings suggest a new classification of tranquilizing agents and propose that studying the secondary conditioned avoidance response may be a useful experimental approach for assessing behavioral drug actions.

Study at a glance

Abstract

Abstract The secondary conditioned response has been studied in rats in an experimental avoidance situation. The activity of seventeen drugs has been tested upon the secondary conditioned response developed on a stable basis after an appropriate period of training. Chlorpromazine, promazine, reserpine and morphine block the secondary avoidance conditioned response as well as the usual avoidance conditioned response, in doses not affecting the motor function. Meprobamate, hydroxyzine, azacyclonol, phenaglycodol and phenobarbitone sodium have no specific inhibitory action on the avoidance conditioned response, but suppress the secondary conditioned response. A specific depression of conditioned behaviour is also produced by mescaline and iproniazid. Barbitone sodium, glutethimide, L1458 and mephenesin inhibit the conditioned responses only at neurotoxic doses. On the basis of these findings a new classification of “tranquillising agents” is proposed. It is also suggested that the systematic study of the secondary conditioned avoidance response of rats, may provide a useful experimental approach for studying the specific behavioural action of drugs.